Mapping Mountains – Trimble Surveys – Arenig

 

27.09.20  Tomen y Mur (SH 705 386)  

Tomen y Mur (SH 705 386)

When I first discovered hill walking one of the joys was winter time.  The shortened daylight hours gave opportunity to open maps and plan routes for the following year.  When looking through these Ordnance Survey maps I remember first coming across references to a Roman Amphitheatre, Roman Road, Roman Fort and Roman Practice Works.  All of which were placed just to the north of Trawsfynydd.  I was intrigued, but the pull of higher hills dominated my perspective for many years to come. 

All of the above relate to a Roman Fort complex known as Tomen y Mur, and today, along with my brother; Bryn, I visited for the first time.  The visit did not disappoint. 

The Fort complex was built during the governance of Gnaeus Julius Agricola in AD 78, and was abandoned around AD 140.  A thousand years later during the Norman period the site was re-occupied and fortified with a Motte within the walls.  It is this Motte that is now the centrepiece of the complex. 

A number of months ago I’d analysed the summit and bwlch of this hill via LIDAR, partly for any prospective future visit, but also to determine the drop value for the hill.  The LIDAR image for Tomen y Mur appears below. 

LIDAR image of Tomen y Mur

We met on the outskirts of Trawsfynydd and then drove the short distance up a minor road to the small car park that serves visitors to the site.  An information board and large stone with the Parc Cenedlaethol Eryri / Snowdonia National Park emblem with the name Tomen y Mur appearing below are positioned beside the parking area, with the information board giving a suggested walking route through the complex. 

The Snowdonia National Park emblem

We’d picked a good day to visit as early autumnal skies were blue and the air had a slight crispness to it.  A gate gave access to the site and a path led toward an old ruined house at the foot of the Motte, which lends itself to the extended name of Castell Tomen y Mur. 

Heading toward the old ruined farm house and the Motte

The Motte dominates the site and rises similar to an ancient Bronze Age burial mound.  Close to its base are the old ruined farmhouse and a reconstructed part of the walled complex. 

Part of the reconstructed wall

Wandering around Tomen y Mur reminded me of one aspect why I love Wales so, as the site has little fanfare and benefits for it.  Today we had the whole complex to ourselves.  With information, if needed, given by a number of unobtrusive interpretation boards, each positioned beside places of importance. 

Approaching the high point of Tomen y Mur

Being here I wanted to survey the high point of the site which nowadays is the top of the Motte.  Steep on all sides and with the signs of a few routes of ascent we plodded up to where the view opened across to the higher Eryli peaks with the near Moelwynion lined one hill after another, and to our south the expanse of Llyn Traswfynydd glistened in the early morning sunshine. 

Bryn at the summit of Tomen y Mur

It only took a few moments to set the Trimble up and gather its allotted data.  Once data were stored I closed the equipment down and savoured the view. 

Gathering data at the summit of Tomen y Mur

We now headed toward the remains of the bath house on a part of the old Roman road of Sarn Helen.  Close by was where this road bridged a stream tributary and you can still make out where the bridge must once have been. 

Our route back took us to the remains of the amphitheatre which is beside the small parking area, and separated from it by a sturdy Welsh stone wall.  We walked its embankments before heading back to the car.  The visit took a leisurely hour and was one I’d recommend. 

 

Survey Result: 

 

Tomen y Mur  

Summit Height:  303.2m (converted to OSGM15, Trimble GeoXH 6000) (significant height revision)

Summit Grid Reference:  SH 70544 38679 (Trimble GeoXH 6000)

Bwlch Height:  288.1m (LIDAR)

Bwlch Grid Reference:  SH 70674 38754 (LIDAR)

Drop:  15.1m (Trimble GeoXH 6000 summit and LIDAR bwlch) (Welsh Sub-P15 reclassified to Welsh P15)

Dominance:  4.99% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

For further details please consult the Trimble Survey Spreadsheet